Raising a wall mounted toilet?

My mom is elderly and lives alone in a co-op. She is getting her bathroom made more handicap friendly, but has been told that there is no way to raise her wall-mounted toilet and there are no high wall mounted toilets. Her current one is about 14" off the floor, she says, and she really needs another 5 or 6 inches. Is there a type of toilet that can be installed for her that would be substantially higher or does she have to continue to use a plastic toilet riser?

The plastic toilet riser seat will be the cheapest solution, otherwise get ready to rip
out the wall & associated plumbing and install the w.c. higher. One of my elderly
parents had the plastic "riser seat" with grab bars. It seemed to work o.k. for them!

The carrier in the wall can be installed at any height (thus changing the seat height)...moving the plumbing and tearing up the wall can be problematic especially if this is back-to-back of another bathroom.